Moving Picture Experts Group-Dynamic Adaptive Streaming over HTTP (hereinafter, referred to as “DASH”) (MPEG-DASH) using the same HTTP as browsing of a web site as an internationally standardized moving image delivery protocol available for moving image delivery via the Internet has been known (for example, see Non-Patent Literature 1).
DASH implements adaptive streaming technology. In other words, a content supply side is configured to prepare a plurality of streams in which content of the same subject is included, and an image quality, an angle of view size, or the like changes according to a communication environment of the internet serving as a delivery path or a capability or a state of a reception side. On the other hand, the reception side can select an optimal stream among the plurality of streams prepared by the supply side according to the communication environment of the Internet, the decoding capability of the reception side, or the like and acquire and reproduce the selected optimal stream.
As described above, in the DASH, a metafile called a media presentation description (MPD) is supplied from the supply side to the reception side so that the reception side can adaptively select and acquire a stream.
An address (url information) of a supply source of streaming data (media data such as audio video/subtitle) of content divided into chunks is described in the MPD. The reception side can access a predetermined server serving as a content supply source based on the url information, requests streaming data, and receives and reproduce streaming data HTTP-unicast-delivered according to the request.
FIG. 1 illustrates an example of a configuration of a content supply system that delivers content in a streaming manner based on the DASH.
A content supply system 10 includes a plurality of content supply devices 20 (in this case, 20A, 20B, and 20C) of a side at which content is supplied and a plurality of DASH clients 30 of a side at which content is received. The DASH clients 30 are connected to the content supply device 20 via a CDN 12 using the internet 11.
The content supply device 20A delivers content of the same subject through a plurality of streams as a channel A. The content supply device 20B delivers content of the same subject different from content of the channel A through a plurality of streams as a channel B. The same applies to the content supply device 20C. Hereinafter, when it is unnecessary to distinguish the content supply devices 20A 20B, and 20C individually, the content supply device is referred to simply as a content supply device 20.
The content supply device 20 includes a content management server 21, a DASH segment streamer 22, and a DASH MPD server 23.
The content management server 21 manages content supplied to the DASH clients 30, generates a plurality of pieces of streaming data having different bit rates from content of the same subject, and outputs the generated streaming data to the DASH segment streamer 22.
The DASH segment streamer 22 temporally divides each piece of streaming data into segments, holds each of the segments as a file, and notifies the DASH MPD server 23 of an address of a supply source of the files. Further, the DASH segment streamer 22 HTTP-unicast-delivers the file of the segmented streaming data in response to a request (an HTTP request) from the DASH client 30, as a WEB server.
The DASH MPD server 23 generates an MPD in which, for example, an address indicating a supply source of files of (segments of) a plurality of pieces of streaming data is described. The DASH MPD server 23 HTTP-unicast-delivers the generated MPD according to the request (the HTTP request) from the DASH client 30 as the WEB server.
The DASH client 30 requests the DASH MPD server 23 to transmit the MPD, request the DASH segment streamer 22 to transmit the streaming data based on the MPD HTTP-unicast-delivered according to the request, and receive and reproduce the file HTTP-unicast-delivered according to the request.
A cache server (not illustrated) is installed on the CDN 12. The cache server caches the MPD or the file of the streaming data which is HTTP-unicast-delivered through the CND 12, and HTTP-unicast-delivers the cached MPD or the like to the DASH client 30 that has transmitted the HTTP request instead of the DASH MPD server 23 serving as the WEB server or the DASH segment streamer 22.